Numerous polythiophenes have been studied extensively due to their interesting electrical and/or optical properties. Polythiophenes become electrically conducting upon chemical or electrochemical oxidation or reduction.
EP-A 257 573 discloses an intrinsically electrically conductive polymer, wherein through connection in the 2-position and/or the 5-position are coupled to one another, statistically averaged from 60 to 100% by weight structural units, which are derived from at least one monomer of the formula (1): in which R1 is a C1-C2-alkoxy group or —O(CH2CH2O)nCH3 with n=1 to 4 and R2 is a hydrogen atom, a C1-12-alkyl group, a C1-12-alkoxy group or —O(CH2CH2O)nCH3 with n=1 to 4, or R1 and R2 together are —O(CH2)m—CH2— or —O(CH2)m—O— with m=1 to 12, 0 to 40% by weight structural units, which are derived from at least one monomer of the formula (2): wherein R4 and R5 are independently of one another a hydrogen atom, a halogen atom, a C1-12-alkyl group or aryl or together with C-atoms connected to them form an aromatic ring, R3 and R6 independently of one another represent a hydrogen atom or R3 together with R4 and the C-atoms connected to them or R5 together with R6 and the C-atoms connected to them each form an aromatic ring, X represents an oxygen atom, a sulfur atom, a ═NH group, a ═N-alkyl group or a ═N-aryl group, 0 to 40% by weight structural units, which are derived from at least one monomer of formula (3): where R7, R8, R9 and R10 independently of one another represent a hydrogen atom, a C1-12-alkyl group, a C1-12-alkoxy group or an aryl group, Y and Z independently of one another represent an oxygen atom, a sulfur atom, a ═NH group, a ═N-alkyl group or a ═N-aryl group, R11 represents an arylene group, a heteroarylene group or a conjugated system of the formula (CH═CH)o, wherein o is 1, 2 or 3, 0 to 40% by weight structural units, which are derived from at least one monomer of formula (4): wherein R12 and R13 independently of one another represent a hydrogen atom, a halogen atom, a C1-12-alkyl group, a C1-12-alkoxy group, a C1-4-alkylamino group or a C1-4-acylamino group, R14 represents a halogen atom, a C1-12-alkyl group, a C1-12-alkoxy group, a C1-4-alkylamino group or a C1-4-acylamino group and X has the meaning given above, wherein the polymer in the oxidized form is completely soluble in dipolar aprotic solvents at 25° C. and solutions with a content of at least 0.1 g of the polymer in 100 mL solvent at 25° C. are obtained.
EP-A 339 340 discloses a polythiophene containing structural units of the formula: in which A denotes an optionally substituted C1-4-alkylene radical and its preparation by oxidative polymerization of the corresponding thiophene.
EP-A 440 957 discloses dispersions of polythiophenes, constructed from structural units of formula (I): in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together form an optionally substituted C1-4-alkylene residue, in the presence of polyanions.
U.S. Pat. No. 5,111,327 discloses an electro-responsive polymer comprising chemically combined repeat units selected from the class consisting of, and a mixture thereof where R is a member selected from hydrogen or a C(1-18) organic radical. Examples 5, 10 and 15 disclose monomers and polymers where R is —CO(CH2)2—COOH.
Stereoregular carboxylic acid-functionalized polythiophenes have been reported by McCullough et al. in 1997 in Journal of the American Chemical Society, volume 119, page 84 and Synthetic Metals, volume 84, page 311. Irregular carboxylic acid-functionalized polythiophenes have been reported in 1990 by Bauerle et al. in Advanced Materials, volume 2, page 490, in 1996 by Englebienne et al. in Journal of the Chemical Society, Chemical Communications, page 1651 and by Masuda et al. in Makromol. Chem., Rapid Communications, volume 13, page 461. Poly(3-(2-(methacryloyl)ethylthiophene was reported by Lowe et al. in 1995 in Macromolecules, volume 28, page 4608.
For a recent overview of the chemistry and properties of poly(3,4-alkylenedioxythiophene) derivatives, see Groenendaal et al. in 2000 in Advanced Materials, volume 12, pages 481-494.
A general drawback of conductive polymers which have been prepared and studied up to now, is that their conductivities are still too low for certain applications, their visible light transmittances are insufficiently high and/or they are not processable.